Convertible air volume control



July 16, 1963 D. L. MORGAN 3,097,604

CONVERTIBLE AIR VOLUME'CONTROL Filed Dec. 13, 1961 INVENTOR DAVID L.MORGAN ATTORNEY United States Patent 3,097,604 CONVERTIBLE AIR VOLUMECONTRDL David Luke Morgan, Shelton, Conn, assignor to Robertshaw-FultonControls Company, Richmond, Va., a corporation of Delaware Filed Dec.13, 1961, Ser. No. 159,099 1 Claim. (Cl. 103-6) This invention rel-atesto a fluid pressure system and more particularly to an air volumecontrol mechanism for supplying air to a liquid storage tank.

In a fluid pressure system, a pressure tank is generally employed toreceive liquid from a pump and store the same under -a predeterminedpressure. To maintain the pressure on the liquid, a layer of air orother gas is confined above the liquid in the tank and this layer of airserves as an expansible cushion. In normal operation of the system, thevolume of air is varied in accordance with changes in the amount ofliquid in the tank and with a decrease in the amount of air, the aircushion is reduced and is replaced by the liquid. As the air cushiondecreases, it is necessary that -a means he provided to restore thepressure such as an air volume control used in conjunction vvith thepump.

One of the objections to prior art air volume control mechanisms is thatconsiderable suction in the system is required to obtain satisfactoryoperation. The present invention eliminates this difiioulty by beingadaptable to be converted for use with either high or low suctionsystems.

It is a primary object of the invention to provide an improved airvolume control for supplying air to -a liquid supply tank.

It is a further object of the invention to provide an air volume controlwhich may be easily converted for use with either a high or low suctionsystem.

Another object of the invention is to provide an improved air volumecontrol which is reliable and inexpensive to manufacture.

Briefly stated, the invention relates to an improved air volume controlfor supplying air to a liquid storage tank and to maintain the desiredair pressure in the tank. A pump is connected to the tank and to asource of liquid to supply liquid to the tank. The air volume controlcomprises a housing for containing air and liquid, a float valvepositioned within the housing and connected to the suction side of saidpump, and a venturi connecting the tank and the housing. A check valveis also provided to connect the throat of the venturi to the surroundingatmosphere. When the pump is operated, the suction created in thehousing causes liquid to be removed from the housing until the floatvalve seats to close the suction outlet. If the liquid level in the tankis above the venturi connection, liquid is drawn through the venturiinto the housing as the liquid level within the housing decreases inresponse to pump suction. The liquid flowing through the venturi createsa suction causing air to be drawn in through the check valve. Stoppingthe pump after the float valve has seated permits liquid to return pastthe float valve into the housing while liquid continues to flow into thehousing through the venturi thus forcing the air through the venturiinto the tank to thereby increase the pressure in the tank.

In another embodiment of the invention, the air volume control may beprovided with a second float valve positioned between the venturi andthe tank to prevent flow of liquid from the tank into the housing whilepermitting air flow in either direction.

Further features, objects, and advantages will become apparent from thefollowing description taken in connection with the accompanying drawingwherein a single figure shows a fragmentary sectional view of a fluid3,097,604 Patented July 16., 1963 pressure system employing the airvolume control of the invention.

Referring to the drawing, the fluid pressure system in general comprisesa liquid storage tank 10, a pump 12, and an improved air volume controlindicated generally at 14. The tank 10 is partially filled with liquidand, above the liquid, is filled with pressurized air. The output sideof pump 12 is connected by conduit 16 to a wall of the tank 10' whilethe pump input side is connected by a conduit 18 to a source of liquid(not shown).

The air volume control 14 includes an air-and-liquidcontaining housing20, which is connected at its lower end by conduit 22 to the suctionside of pump 12,; and which is connected at its upper end to the tank 10by means of horizontally arranged venturi 24 and conduit 26. Liquid flowout of housing 20- through conduit 22 may be controlled by a suitablevalve such as ball float valve 28, which seats in the upper end ofconnection 30 when the liquid level within the housing is no longersuflicient to carry the float valve. A suitable perforated retainingmember 32 may be secured to the upper end of connection 30 to guide thefloat valve 28 to seat on the connection when the liquid level issufficiently decreased. The retaining member 32 also limits the upwardmovement of the float 28 while its perforations permit liquidcommunication between the connection 30 and the inside of the housing20.

Liquid flow from the tank 10 to the housing 20 is prevented by asuitable valve such as ball float valve 34 positioned in an enlargedportion 36 in the end of venturi 24 leading to the tank 10. When thereis sufficient liquid in the enlarged portion 36 and tank pressure isgreater than housing pressure, float 34 seats against the associated endof venturi 24 to prevent liquid flow into the housing. A retaining ring38 may be provided to prevent float 34 from moving out of the enlargedportion 36 toward tank 10. It will be appreciated that the float valve34 permits air flow in either direction.

In accordance with the invention, the throat 25 of venturi 24 isconnected to the surrounding atmosphere by an intersecting passage 40leading to a bored connection 42 positioned in the exterior wall ofventuri 24 and carrying a suitable check valve 44. The connection 42 iscentrally bored to form an atmosphere opening 46 and a larger alignedinlet bore 48 separated by a larger chamber 50 in which the movablevalve 44 is loosely positioned. As is illustrated in the drawing, anaperture 52 in valve 44 is offset from its central axis so as to beengageable with the upper wall defining the chamber 50. The check valve44 is made of many suitable resilient material so as to be deformableunder pressure and thus moved away from the upper wall of chamber 50 andestablish communication between the opening 46 and the bore 48 throughthe offset aperture 52. With such an arrangement, the check valve 44permits air flow from the atmosphere in the venturi when the properpressure differential exists.

Turning now to the operation of the air volume control, assume firstthat the pump 12 is ofi and that the liquid in the tank 10 is at thehigh level marked H in the drawing. At such level, the housing 20 isalso filled with liquid, which is the normal condition for the housing20 when the pump 12 is not operating. If the air pressure above theliquid in the tank 10 is below a predetermined limit, the pump 12 may bestarted, in response to a pressure switch or other suitable means, notshown, to increase the air pressure. The suction created by the pump 12will cause the liquid in housing 20 to be drawn out of the housing pastthe float valve 28, which will be floating in the upper portion ofretaining member 32. The pressure diiferential between the tank 10 andthe housing 20 and the presence of liquid in enlarged portion 36 of theventuri 24 will cause the float valve 34 to seat against the venturi,thereby preventing liquid flow from the tank 10 to the housing 20. Asthe liquid is withdrawn from the housing 20, air will be drawn inthrough check valve 44. When substantially all of the liquid has beenremoved from the housing, float valve 28 guided by retaining member 32will seat against the upper end of connection 30 preventing air frombeing removed from the housing. After the pump 12 stops, in response toa suitable tank pressure switch, the pressure on opposite sides of pump12 will soon equalize causing liquid to again enter housing 20 past thefloat valve 28. This action will pressurize the air in the housing 20causing it to be forced past the float valve 34 into the tank 10 tothereby increase the pressure above the liquid.

If when the pump is started, the liquid in the tank 10 is at a levelbelow the conduit 26 such as indicated at L in the drawing, air from thetank will be drawn past the float valve 34 into the housing. After theliquid level in the tank has been raised sufliciently to close floatvalve 34 and the pump is stopped, the control 14 will operate asdescribed in the preceding paragraph to pressurize the tank liquid.

In accordance with the invention, the air volume control shown in thedrawing may be easily converted to form a modified control requiringless suction than the control heretofore described. This may beaccomplished by merely removing the float valve 34 and its retainingring 38. With the valve 34 removed, the housing 20 will of course be indirect communication with the tank 10. If the liquid in the tank isabove the connection of conduit 26 such as at H and the pump 12 isstarted, the pressure differential will cause liquid to flow through theventuri 24 as liquid is drawn from the housing 20.

Liquid flow through the venturi 24 will create a vacuum in the throat ofthe venturi causing air to be drawn in past check valve 44 into housing20. This process will continue until all the liquid is effectivelyremoved from the housing and float valve 28 seats to close the outlet.Liquid will continue to flow through venturi 24 from the tank 10 to thehousing 20 until the housing pressure equals tank pressure. As thepressure is being equalized, the buoyancy of the air will cause it to bedisplaced through the venturi into the tank. It will be appreciated thatthe water passing through the venturi 24 provides the suction forbringing in the air rather than the pump 12. Consequently less suctionis required to operate the control 14 when valve 34 is removed.

If, before the pump 12 is started, the liquid level is at L, air fromthe tank will flow through the venturi and enter housing 20; but sincethe air will only flow fast enough to replace the liquid being drawnfrom the housing, the pressure drop across the venturi will not besuflicient to cause an appreciable vacuum in the throat. Consequently noair will enter through the check valve until the liquid level in thetank is raised, and at which time the control will function as describedin the preceding paragraph.

Thus, it will be appreciated that an air volume control has beenillustrated and described that may easily be converted to a modifiedform of control. As it will be obvious to those skilled in the art thatvarious changes and modifications may be made in order to adapt it todiflerent conditions without departing from the scope hereof, it isintended that all matter contained in the above description or shown onthe accompanying drawing be interpreted as illustrative and not in alimiting sense.

What is claimed is:

In a fluid pressure system, the combination including a fluid storagetank, a pump for supplying liquid to said tank, and air volume controlmeans for maintaining a desired air pressure in said storage tankcomprising a housing containing fluids of liquid and air and having portmeans adjacent its top and bottom, means connecting the bottom portmeans of said housing to the suction side of said pump whereby operationof said pump causes a flow of liquid through the bottom port means,valve means including a ball float valve operative in response to apredetermined liquid level in said housing for controlling the flow ofliquid through said bottom port means, horizontal conduit meansconnecting the top port means of said housing to said storage tank,venturi means having a venturi throat in said conduit means, an enlargedchamber in said conduit means between one end of said venturi means andsaid tank, a ball float valve in said enlarged chamber cooperating withthe said one end of said venturi means to prevent flow of liquid fromsaid tank to said venturi means, bored fitting means vertically carriedby said conduit means and including a passage perpendicularlyintersecting said venturi throat for establishing communication betweenthe atmosphere and said venturi throat, an atmosphere opening on one endof said bored' fitting means and an inlet bore on the opposite endthereof having a larger diameter than said atmosphere opening, a checkvalve chamber intermediate said atmosphere opening and said inlet borehaving a larger diameter than said inlet bore, a check valve disc ofresilient material loosely disposed in said check valve chamber forsealing said atmosphere opening, and a flow passage in said check valvedisc being offset from said atmosphere open-ing and permitting an airflow to said venturi throat when said check valve disc is moved awayfrom said atmosphere opening.

References Cited in the file of this patent UNITED STATES PATENTS2,421,237 Bergh May 27, 1947 2,621,597 Armstrong Dec. 16, 1952 2,748,798Withrow June 5, 1956 2,839,001 Tubbs June 17, 1958

